An organic electroluminescence device (hereinafter also referred to simply as “organic EL device”) is considered promising with respect to its use as a solid-state light-emitting, inexpensive, large-area full-color display device and is now under intense development. The organic EL device generally has a structure that an anode (ITO), a hole transport layer, an organic layer (luminescent layer), an electron transport layer and a cathode are laminated in this order on a transparent substrate such as a glass plate and a sealing can is placed on the surface. The above organic layer (luminescent layer), hole-injection layer, hole transport layer and electron transport layer (hereinafter also referred to simply as “organic layer and the like”) contain organic EL device materials. As the organic EL device materials, low-molecular-weight materials such as copper phthalocyanine (CuPc), star-burst, bis(N-(1-naphthyl)-N-phenyl)benzidine, a beryllium-quinoline complex (Beq2), 4-methyl-8-hydroxyquinoline and a 3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole molecule and high-molecular-weight materials such as poly(p-phenylenevinylene) and polyaniline are known.
In a production process of the organic EL device using the low-molecular-weight material as the organic EL material, the organic layer and the like are formed by vacuum-depositing the organic EL device material on a substrate having the anode layer, and the hole injection layer as required, formed thereon. When the organic layer and the like are formed by vacuum deposition, patterning is required for each pixel so as to display each color or control unwanted light emission. For this patterning, a metal mask having slits is used (refer to Japanese Patent Laid-Open Publication Nos. 2003-332057 and 2003-297566).
When the organic layer is formed in accordance with the above deposition technique, the organic EL device material adheres to a surface of the metal mask. When the metal mask continues to be used with the organic EL device material adhering thereon, the metal mask itself is deformed or the accumulated organic EL device material clogs the slits, with the result that high-precision patterning is no longer possible. Accordingly, to use the metal mask over and over, it must be cleaned on a regular basis to remove the organic EL device material adhering on its surface. As cleaning agents and cleaning methods which may be used for the above purpose, a method of wiping out the organic EL material by a hand using an organic solvent such as acetone, chloroform, isopropyl alcohol or methylene chloride and a method of washing out the organic EL material by using a supercritical fluid at high pressure are known, for example (refer to Japanese Patent Laid-Open Publication No. 2003-305421).
While the above method of cleaning the metal mask having the organic EL device material adhering thereon by use of a supercritical fluid has an advantage that recycling of the organic EL device material is possible, the method not only requires a pressure device but also has problems with respect to cleaning efficiency and operability.
Meanwhile, an automatic system can be built to clean an apparatus or article having the organic EL device material adhering thereon by use of a cleaning agent and is an industrially advantageous method as can be understood from a fact that it is used in many fields. However, cleaning using an organic solvent such as acetone, chloroform, isopropyl alcohol or methylene chloride is considered problematic with respect to environmental problems and safety on human bodies. Therefore, for cleaning an apparatus or article having the organic EL device material adhering thereon by use of a cleaning agent, it is necessary not to use an organic solvent which has an adverse effect on the environment and human bodies such as acetone, chloroform, isopropyl alcohol or methylene chloride but is necessary to find a cleaning agent having high detergency on the organic EL device material.
Meanwhile, a magnetic head device, a liquid crystal panel device or a semiconductor device such as an IC or LSI is formed by coating a resist on a conductive metal thin film or an insulation film such as an SiO2 film or SiN film which is formed on a substrate, exposing the coated resist via a mask having a desired pattern formed thereon and developing the resist to form a resist pattern in a desired region, carrying out a treatment such as etching by use of the resist pattern as a mask and then removing the resist.
As a cleaning/removing agent for removing the above resist, an alkaline cleaning/removing agent comprising a water-soluble organic amine as an essential component has heretofore been used. As such a cleaning/removing agent, a resist stripping agent comprising (a) an amine such as monoethanolamine or ethylenediamine, (b) a polar solvent such as dimethyl sulfoxide or N-methyl-2-pyrrolidone and (c) a surfactant is known (refer to Japanese Patent Laid-Open Publication No. 63-231343), and the cleaning/removing agent shows excellent resist removability. However, in recent production of a magnetic head device, liquid crystal panel device and semiconductor device, the cleaning/removing agent is used at a high temperature of, for example, 80 to 90° C. in some cases, and in such a case, there is a problem that an insoluble matter which is difficult to remove even in a subsequent rinsing step is deposited on the surface of a cleaned object. In view of the above problem, a resist cleaning/removing agent comprising dimethyl sulfoxide and ethylenediamine has been proposed as a cleaning agent free of such a problem (refer to Japanese Patent Laid-Open Publication No. 11-133628). This cleaning agent does not have a problem that an insoluble matter is deposited on the surface of a cleaned object even when it is used at high temperatures and shows excellent resist removability. However, since the cleaning agent contains ethylenediamine which is highly irritating to the skin and eyes and has high sensitization, a safer cleaning agent has been desired.
Meanwhile, resist removing agents which do not comprise a water-soluble organic amine as an essential component are also known. Illustrative examples of such cleaning agents include a resist cleaning/removing agent comprising at least 50% by mass of dimethyl sulfoxide and 5 to 50% by mass of alcohol (refer to Japanese Patent Laid-Open Publication No. 63-163457) and a resist stripping agent comprising dimethyl sulfoxide, amino alcohol and water (refer to Japanese Patent Publication No. 7-69619).
These cleaning/removing agent and stripping agent show excellent resist removability. However, the former resist cleaning/removing agent has a problem of low flash point which limits its cleaning conditions and handling. Meanwhile, the latter resist stripping agent has a problem that it may cause corrosion of conductive film which may result in breaking of wires when a substrate having the conductive film formed thereon is used as an object to be cleaned, since the resist stripping agent contains water.
Recently, the material of conductive films has been shifted to aluminum and copper which are liable to corrode. They are susceptible to corrosion by water, and this disadvantage leads to a severe problem, i.e. a decrease in product yield. Further, although pyrrolidone typified by N-methyl-2-pyrrolidone, ketone typified by acetone and methyl ethyl ketone and methylene chloride have been widely used as components of cleaning agents because they exert high detergency, use of these materials tends to be avoided from the viewpoints of environmental problems and safety on human bodies.